1. Field of the Invention
The present invention relates to a camera with a focal plane shutter and more particularly the present invention is directed to an additional light shielding device for such focal plane shutter comprising a group of opening blades and a group of closing blades able to cover the whole area of aperture by a combination of these blades.
2. Description of the Prior Art
The reflection photometry is well known in the art and various systems for carrying out this TTL reflection photometry have already been proposed. According to TTL reflection photometry, the light transmitted through a photographing lens is reflected upon the surface of a focal plane shutter and the reflected light is measured photometrically. The above-mentioned type of focal plane shutter consisting of a group of opening blades and a group of closing blades is generally called a divided type focal plane shutter. It is a common knowledge in the art that the application of the above-mentioned reflection photometry system to the divided type focal plane shutter involves some difficult problems. One of the most important problems is leakage of light. Since a plural number of shutter blades cover the film, the light can come in through each overlapping portion of neighbouring blades. This is particularly true for a range finder type of camera which has no member serving as a shade such a quick return mirror between the photographing lens and the shutter blades. In the range finder type of camera, therefore, the light transmitted through the photographing lens enters the shutter directly, which enhances the problem of light leakage. This brings forth a particular difficulty when the reflection photometry system is applied to such type of camera.
The same problem arises also in case of the so-called direct photometry according to which the light reflected upon both the shutter surface and the film surface is measured photometrically. For direct photometry it is desired to increase the reflection power of the shutter up to a value nearly equal to that of the film surface. However, such increase of reflection power of the shutter results in increase of leak light. Therefore, in practice, it is very difficult to apply the direct photometric system to the divided type focal plane shutter.